The invention refers to a centrifugal apparatus, and in particular, but not exclusively to a flow-through centrifugal apparatus in which materials are to be centrifuged while flowing through in continuous communication, for example for blood or plasma processing.
One problem with respect to centrifugal flow-through systems is to establish continuous fluid flow communication between a stationary feeding terminal and a discharged terminal at the revolving fluid processing chamber. The relative movement of the two terminals causes a twisting of the connecting tube. Therefore, in case of conventional flow-through centrifugal systems rotating seals or couplings are used for the connection at the terminals. The manufacturing of such rotating seals is expensive, and normally under the action of rotation they give off particulate matter from the seal material which may lead to leaking spots at the connecting terminals. Especially for processing blood, the use of rotating seals is problematical as defects and leaks can cause contamination of the ambience as well as of the blood to be processed. Furthermore, the fragile components of blood, particularly thrombocytes, can be damaged while passing through the high friction or turbulence caused by a rotating seal.
In order to solve these problems it is known from German Auslegeschrift No. 2,114,161 to establish connections between rotating and stationary parts in such a way that to avoid twisting or drilling the use of rotating seals or slip rings is not required. For this purpose the tube--or for centrifugal apparatusses not of the flow-through type, generally the cable--is led from the stationary terminal overlapping the rotating part in a loop which is revolved around the rotating part at half the angular velocity of the processing or separation chamber, and in the same direction. For establishing this system derived from the spinning-mill technology a stationary gear rim is mounted onto a stationary basic structure coaxially through which extends a shaft driven by a motor. On this shaft a hollow cylinder is mounted which rotates unison with the shaft, the cylinder having a gear wheel laterally offset with respect to the axis of rotation meshing with the stationary gear rim and riding on the stationary gear rim when the hollow cylinder is rotating. Further mounted at the hollow cylinder is a laterally offset auxiliary shaft also equipped with gears on top and bottom thereof, the lower gear meshing with the first gear wheel and being rotated thereby. The upper gear, keyed to the auxiliary shaft as well as the lower gear and rotating in unism therewith, transmits its rotating movement to a drive gear of a revolving chamber, i.e. the processing chamber in the case of a flow-through centrifugal apparatus, which is mounted coaxially to the shaft driven by the motor. The transmission ratio of the described gear arrangement is selected in such a way that the hollow cylinder moves with half the angular velocity and in the same direction as the processing chamber thus twisting or drilling of the connecting flexible tube or a cable is avoided. A disadvantage in the known arrangement is in general the use of toothed gears. Due to such gear arrangement the production of the centrifugal apparatus has to be effected with high precision, and, therefore, is complicated and expensive. In addition, gears need maintenance, e.g. have to be lubricated, and are relatively noisy in operation. A further disadvantage consists in obtaining the drive of the processing chamber from the revolving gear wheel riding on the stationary gear rim. Due to this, the direction of the gear rotation is opposed to that of the hollow cylinder. In order to obtain the required movement consistent with the direction of rotation of the hollow cylinder, an additional gear is necessary for nothing but the reversion of the direction of rotation, this also increasing the noise level, the maintenance frequency and expenditure, and the cost of production due to the necessity of high precision.
In order to reduce the noise of centrifugal apparatusses driven by toothed gears and to compensate production tolerances in the driving units, it is further known from German Offenlegungsschrift No. 2,612,988 to drivingly connect the individual shafts by means of drive belts. In principle, however, the basic construction as above described remains unchanged. Therefore, also here a stationary pulley is provided in succession to the motor drive unit, and to this pulley a drive belt is coupled which on the other hand is coupled to a laterally offset pulley revolving together with the hollow cylinder causing the movement of the fexible tube loop. The revolving movement of this pulley is, by having the drive belt coupled to the stationary pulley as center of revolution of the revolving pulley, transferred into a rotational movement of the latter pulley fitted to the hollow cylinder thus providing drive to the processing chamber. As in the case of the arrangement described before, also here the driving movement for the processing chamber is provided in opposite rotational direction than required, and has to be reversed into the required rotational direction by means of auxiliary shafts with auxiliary pulleys resulting in producing twice the angular velocity of the hollow cylinder in the required direction. The construction is generally complicated and expensive, and it can lead to fairly big and heavy rotating parts. In addition, the high centrifugal forces thus produced have to be controlled, which, due to the large loop of the connecting flexible tube, become greater and produce more stress also in the tube. For twisting or detwisting of the connecting tube its loop may be guided in eyelets or rings along the rotatable hollow cylinder. In case of larger tube loops, as required in the afore-mentioned systems because of the necessary units for reversing the rotational direction, the tubes are relatively heavily stressed at the terminals, in particular due to centrifugal forces and simultaneous friction. To eliminate this, it is further known from German Offenlegungsschrift No. 2,611,307 to firmly hold the loop on its outer side and to detwist it by means of a detwisting unit linked to the drive via a toothed belt. This construction is complicated and leads to a complicated and expensive arrangement of the centrifugal apparatus.